Download packages to temp dir inside system cache.

utils/pub/hosted_source.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library hosted_source;
 
 import 'dart:io' as io;
 import 'dart:json';
 import 'dart:uri';
 
@@ skipping 59 matching lines @@
     var parsedDescription = _parseDescription(id.description);
     var name = parsedDescription.first;
     var url = parsedDescription.last;
 
     var fullUrl = "$url/packages/$name/versions/${id.version}.tar.gz";
 
     print('Downloading $id...');
 
     // Download and extract the archive to a temp directory.
     var tempDir;
-    return Futures.wait([httpGet(fullUrl), createTempDir()]).chain((args) {
+    return Futures.wait([httpGet(fullUrl),
+                         systemCache.createTempDir()]).chain((args) {
       tempDir = args[1];
       return timeout(extractTarGz(args[0], tempDir), HTTP_TIMEOUT,
           'Timed out while fetching URL "$fullUrl".');
     }).chain((_) {
       // Now that the install has succeeded, move it to the real location in
       // the cache. This ensures that we don't leave half-busted ghost
       // directories in the user's pub cache if an install fails.
       var rename = renameDir(tempDir, destPath);
 
       // TODO(rnystrom): Awful hack. On Windows, we see cases where the extract
@@ skipping 62 matching lines @@
 
     var name = description["name"];
     if (name is! String) {
       throw new FormatException("The 'name' key must have a string value.");
     }
 
     var url = description.containsKey("url") ? description["url"] : defaultUrl;
     return new Pair<String, String>(name, url);
   }
 }